// Operates NanoUI
/obj/item/modular_computer/ui_interact(mob/user, ui_key = "main", var/datum/nanoui/ui = null, var/force_open = 1)
	if(!enabled)
		if(ui)
			ui.close()
		return 0
	if(!use_power())
		if(ui)
			ui.close()
		return 0

	// Robots don't really need to see the screen, their wireless connection works as long as computer is on.
	if(!screen_on && !issilicon(user))
		if(ui)
			ui.close()
		return 0

	// If we have an active program switch to it now.
	if(active_program)
		if(ui) // This is the main laptop screen. Since we are switching to program's UI close it for now.
			ui.close()
		active_program.ui_interact(user)
		return

	// We are still here, that means there is no program loaded. Load the BIOS/ROM/OS/whatever you want to call it.
	// This screen simply lists available programs and user may select them.
	var/obj/item/computer_hardware/hard_drive/hard_drive = all_components[MC_HDD]
	if(!hard_drive || !hard_drive.stored_files || !hard_drive.stored_files.len)
		to_chat(user, "<span class='danger'>\The [src] beeps three times, it's screen displaying a \"DISK ERROR\" warning.</span>")
		return // No HDD, No HDD files list or no stored files. Something is very broken.

	ui = SSnanoui.try_update_ui(user, src, ui_key, ui, force_open)
	if(!ui)
		var/datum/asset/assets = get_asset_datum(/datum/asset/simple/headers)
		assets.send(user)
		ui = new(user, src, ui_key, "computer_main.tmpl", "NTOS Main menu", 400, 500)
		ui.set_auto_update(1)
		ui.set_layout_key("program")
		ui.open()


/obj/item/modular_computer/ui_data(mob/user)
	var/list/data = get_header_data()
	data["programs"] = list()
	var/obj/item/computer_hardware/hard_drive/hard_drive = all_components[MC_HDD]
	for(var/datum/computer_file/program/P in hard_drive.stored_files)
		var/running = 0
		if(P in idle_threads)
			running = 1

		data["programs"] += list(list("name" = P.filename, "desc" = P.filedesc, "running" = running))

	return data

// Function used by NanoUI's to obtain data for header. All relevant entries begin with "PC_"
/obj/item/modular_computer/proc/get_header_data()
	var/list/data = list()

	var/obj/item/computer_hardware/battery/battery_module = all_components[MC_CELL]
	var/obj/item/computer_hardware/recharger/recharger = all_components[MC_CHARGE]

	if(battery_module && battery_module.battery)
		switch(battery_module.battery.percent())
			if(80 to 200) // 100 should be maximal but just in case..
				data["PC_batteryicon"] = "batt_100.gif"
			if(60 to 80)
				data["PC_batteryicon"] = "batt_80.gif"
			if(40 to 60)
				data["PC_batteryicon"] = "batt_60.gif"
			if(20 to 40)
				data["PC_batteryicon"] = "batt_40.gif"
			if(5 to 20)
				data["PC_batteryicon"] = "batt_20.gif"
			else
				data["PC_batteryicon"] = "batt_5.gif"
		data["PC_batterypercent"] = "[round(battery_module.battery.percent())] %"
		data["PC_showbatteryicon"] = 1
	else
		data["PC_batteryicon"] = "batt_5.gif"
		data["PC_batterypercent"] = "N/C"
		data["PC_showbatteryicon"] = battery_module ? 1 : 0

	if(recharger && recharger.enabled && recharger.check_functionality() && recharger.use_power(0))
		data["PC_apclinkicon"] = "charging.gif"

	switch(get_ntnet_status())
		if(0)
			data["PC_ntneticon"] = "sig_none.gif"
		if(1)
			data["PC_ntneticon"] = "sig_low.gif"
		if(2)
			data["PC_ntneticon"] = "sig_high.gif"
		if(3)
			data["PC_ntneticon"] = "sig_lan.gif"

	if(idle_threads.len)
		var/list/program_headers = list()
		for(var/I in idle_threads)
			var/datum/computer_file/program/P = I
			if(!P.ui_header)
				continue
			program_headers.Add(list(list(
				"icon" = P.ui_header
			)))

		data["PC_programheaders"] = program_headers

	data["PC_stationtime"] = station_time_timestamp()
	data["PC_showexitprogram"] = active_program ? 1 : 0 // Hides "Exit Program" button on mainscreen
	return data


// Handles user's GUI input
/obj/item/modular_computer/Topic(href, list/href_list)
	if(..())
		return
	var/obj/item/computer_hardware/hard_drive/hard_drive = all_components[MC_HDD]
	switch(href_list["action"])
		if("PC_exit")
			kill_program()
			return 1
		if("PC_shutdown")
			shutdown_computer()
			return 1
		if("PC_minimize")
			var/mob/user = usr
			if(!active_program || !all_components[MC_CPU])
				return 1

			idle_threads.Add(active_program)
			active_program.program_state = PROGRAM_STATE_BACKGROUND // Should close any existing UIs

			active_program = null
			update_icon()
			if(user && istype(user))
				ui_interact(user) // Re-open the UI on this computer. It should show the main screen now.

		if("PC_killprogram")
			var/prog = href_list["name"]
			var/datum/computer_file/program/P = null
			var/mob/user = usr
			if(hard_drive)
				P = hard_drive.find_file_by_name(prog)

			if(!istype(P) || P.program_state == PROGRAM_STATE_KILLED)
				return 1

			P.kill_program(forced = TRUE)
			to_chat(user, "<span class='notice'>Program [P.filename].[P.filetype] with PID [rand(100,999)] has been killed.</span>")

		if("PC_runprogram")
			var/prog = href_list["name"]
			var/datum/computer_file/program/P = null
			var/mob/user = usr
			if(hard_drive)
				P = hard_drive.find_file_by_name(prog)

			if(!P || !istype(P)) // Program not found or it's not executable program.
				to_chat(user, "<span class='danger'>\The [src]'s screen shows \"I/O ERROR - Unable to run program\" warning.</span>")
				return 1

			P.computer = src

			if(!P.is_supported_by_hardware(hardware_flag, 1, user))
				return 1

			// The program is already running. Resume it.
			if(P in idle_threads)
				P.program_state = PROGRAM_STATE_ACTIVE
				active_program = P
				idle_threads.Remove(P)
				update_icon()
				return

			var/obj/item/computer_hardware/processor_unit/PU = all_components[MC_CPU]

			if(idle_threads.len > PU.max_idle_programs)
				to_chat(user, "<span class='danger'>\The [src] displays a \"Maximal CPU load reached. Unable to run another program.\" error.</span>")
				return 1

			if(P.requires_ntnet && !get_ntnet_status(P.requires_ntnet_feature)) // The program requires NTNet connection, but we are not connected to NTNet.
				to_chat(user, "<span class='danger'>\The [src]'s screen shows \"Unable to connect to NTNet. Please retry. If problem persists contact your system administrator.\" warning.</span>")
				return 1
			if(P.run_program(user))
				active_program = P
				update_icon()
			return 1
		else
			return

/obj/item/modular_computer/nano_host()
	if(physical)
		return physical
	return src